We propose three aims to study the effects over two years of moderate to severe traumatic brain injury (TBI) relative to orthopedic injury (OI) in children on: (1) change in cognitive control and motivation, including different forms of inhibition, working memory, flexible allocation of cognitive resources, and response to incentives; (2) change in social cognition, including processing of emotional expression and intentionality; (3) change in cognitive control and social cognition in relation to change in outcome domains of executive functioning in everyday activities, academic achievement, and psychosocial adjustment. We also propose to study change in cognitive control and social cognition in relation to age at injury, TBI severity, brain regional volumes, and brain lesion volumes measured from magnetic resonance imaging (MRI) performed at 3 and 18 months postinjury. We would evaluate the moderating effects of family environment (socioeconomic level, stressors and social resources) and control for the effects of preinjury trauma exposure, posttraumatic stress, and depressive symptoms. Children age 7-16 years who sustain a moderate to severe TBI (n=92) or OI (n=92) would be studied at baseline (within 1 month postinjury) and followed-up at 3, 12, 18, and 24 months postinjury. Cognitive control tasks include the Flanker (interference and no-go), Sternberg Item Recognition (interference and working memory), stop signal (stopping a response), selective learning- switching and expository discourse (selectivity in learning items belonging to highly rewarded categories), a modified Iowa Gambling Task, and a prospective memory task with an extrinsic reward manipulation. Social cognition is evaluated by processing facial and prosodic emotional expression and intentionality is assessed by differentiating real from apparent emotion and interpreting the movements of animated figures. Brain regional volumes would be measured by manual tracing and segmentation of gray and white matter for: (1) frontal subregions including lateral, ventromedial, and superior medial regions; (2) amygdala; (3) superior temporal gyrus; and, (4) whole brain. We will also analyze the effects of focal lesion volume and depth in these regions. Outcome measures would be the Woodcock-Johnson III Tests of Achievement, the Brief Behavior Inventory of Executive Function, the Behavior Assessment System for Children, and the Vineland Adaptive Behavior Scale. Statistical analysis of the hypotheses would use general linear mixed models.